1. Field of the Invention
The present invention relates generally to connecting structures for articles of furniture, and more specifically to connecting structures for assembling an article of furniture, such as a chair, and utilizing tubular parts made of a cardboard material.
2. Background Information
Furniture connecting structures using pipes made of a metal material, such as forelegs and back legs of chairs, are known. Legs for chairs and other types of furniture have also been fabricated using a cardboard material. For example, JP-A-61-48312 discloses a chair using hollow cardboard square tubes so that even children can handle. JP-UM-A-48-57319 proposes a chair and rack for storage formed of long cardboard tubes.
However, various problems arise in connecting structures for furniture when, as a joint for connecting pipe-like cardboard tubes, an L-shaped joint having a pipe material curved in an L-shape is used for connection. Namely, when the front end of a cardboard tube is inserted into the joint curved in an L-shape, the front end abuts against the curved inner face and cannot move further forwardly. Accordingly, the connection portion of the cardboard tube with the joint is shortened, whereby it is likely to become loose and the connection strength is lowered.
When the joint and the cardboard tube are fixed with a fitting screw, if a force is applied in such a direction acting to rotate the cardboard tube, a load concentrating at the fitting screw portion is large enough such that the fitting screw portion becomes subjected to breakage. To avoid such problem, in the chair disclosed in JP-A-61-48312 a square columnar insertion portion bent at a right angle is formed as a joint, and the cardboard tube is formed in a hollow square columnar shape so that it can be inserted into this insertion portion. Further, in the chair proposed in JP-UM-A-48-57319, at the side portion of a cylindrical connecting device, a projection protruding in a direction at a right angle is disposed, and a long cardboard tube is inserted thereinto. Accordingly, in JP-A-61-48312 and JP-UM-A-48-57319, the chairs are fabricated using connecting joint portions formed only at right angles such that loads are applied perpendicularly to legs, thereby reducing the possibility of breakage as noted above.
Thus, while it has been possible to fabricate a chair using a cardboard tube connecting structure such that loads are applied perpendicularly to the chair legs, it has been difficult to fabricate chairs using cardboard tube connecting structures with connecting joint portions other than at right angles such as, for example, a chair having a slanting leg or a chair having a corner portion curved in an L-shape, like for conventional folding chairs with legs made of metal pipes. Furthermore, the conventional folding chairs have such a risk that children's fingers are nipped by a movable portion during handling of the folding chairs. Additionally, the conventional chairs made of cardboard tube connecting structures lack sufficient strength and durability.